Rep. Jason Altmire (D-Pa.) may be barred from running in the Democratic primary against fellow Rep. Mark Critz (D-Pa.), a move that would make it all but impossible for him to return to Congress next fall.

A judge will rule Monday whether Altmire submitted enough valid signatures in his petition to get on the ballot, and he is dangerously close to falling below the needed number.

The two were thrown into the same congressional district in redistricting, and their primary has already been testy. Altmire has represented more of the new district, but many unions are furious with him for his health care vote and have rallied around Critz. The primary is expected to be a dog-fight — if it happens.